Cyclodextrin is a cyclic oligosaccharide in which at least six glucose units combine together through .alpha.-1,4 linkage, and those having 6, 7 or 8 glucose units are particularly well known. There are many documents known regarding their applications. All these known applications utilize the selective inclusion ability of cyclodextrin due brought about by the hydrophobic nature of the inside of the cyclodextrin ring and also by the fact that the size of said ring depends on the number of glucose units; cyclodextrin is currently used as a packing for chromatographic separation, as a catalyst, as a masking agent for the off-taste or foul smell of foods, as an agent for retaining volatile materials or for solubilizing sparingly soluble materials, and the like.
One will readily anticipate that such selective inclusion ability of cyclodextrin provides an effective means for separating and extracting hydrophobic materials; however, cyclodextrin is water-soluble, and therefore, cyclodextrin is not suitable for use as a separating or extracting agent since it is difficult not only to separate inclusion compounds from the reaction mixture but also to separate the included compound from cyclodextrin.
If cyclodextrin is immobilized on a polymer, etc. with retaining its inclusion ability, it may be packed in a column and a component of interest may be easily separated, recovered or removed by an adsorption/desorption procedure or by a chromatographic procedure as with ion exchange resins or activated carbon.
Various approaches have been attempted to immobilize cyclodextrin; however, all of them have been unsatisfactory for effective use in industry, because of low utilizability of the immobilized cyclodextrin, insufficient selectivity due to the adsorption of hydrophobic materials by the matrix polymer having immobilized cyclodextrin, and the great cost involved in the preparation thereof.
For example, Examined Japanese Patent Publication Nos. 27083/1980, 41643/1980 and 15806/1981 describe processes for producing polystyrene based polymers containing cyclodextrin derivatives. According to these processes, one unit of cyclodextrin derivative can always be immobilized with respect to one styrene monomer unit. In the case of polymer however, the reactivity thereof is low and the extent of immobilization is not sufficient. Further, Japanese Unexamined Patent Publication Nos. 75402/1980 and 314201/1988 disclose methods in which cyclodextrin is immobilized by subjecting it to a polymer reaction either at a site of glycidyl group or at a site where its epoxy ring is opened. However, even in these methods, the reaction must be carried out for a long time period in order to bind an adequate amount of cyclodextrin to the matrix. Further, the ratio of cyclodextrin actually immobilized is only a part of the total amount charged, and it is impossible to ensure that one cyclodextrin molecule is always immobilized per monomer unit and there have been economic problems to utilize excellent inclusion ability of cyclodextrin for various purposes.
An object, therefore, of the present invention is to provide a process for producing a CD derivative which can be used as a starting material for producing a polymer containing immobilized CD and which has only one protected hydroxyl group among several hydroxyl groups in CD.
Another object of the present invention is to provide a process for producing a polymer containing immobilized cyclodextrin which has one unit of immobilized cyclodextrin derivative per monomer unit, for example, an .alpha.,.beta.-unsaturated acid halide or an .alpha.,.beta.-unsaturated acid having a terminal isocyanate group and which shows high reactivity even in the polymer reaction.